This invention relates generally to systems for monitoring one or more physical properties, such as temperature or oxygen content by means of sensing transducers which each have unique signal generating characteristics, and more particularly, to an arrangement for quickly and accurately calibrating a signal conditioner to operate with such sensing transducers.
Monitoring systems for sensing temperature, oxygen or other physical properties are well known and used, for example, in the medical field for critical care units. Such systems monitor a physical property by means of a sensing transducer which generates raw signals representative of the physical property. The raw signals are passed to a signal conditioner which is coupled to the sensing transducer, with the signal conditioner converting the raw signals into a human-readable form for use by personnel utilizing the monitoring system.
Some sensing transducers generate sufficiently consistent signals from one transducer to another that they may be readily interchanged upon failure of the transducer or for disposal. However, many other sensing transducers are not readily interchangeable since they have unique signal generating characteristics which must be provided to the signal conditioner for the signal conditioner to accurately process or transform the raw signals from the sensing transducers to an accurate human-readable form.
The problems of associating such noninterchangeable sensing transducers with signal conditioners has plagued designers and users of monitoring systems for years. These problems have been greatly reduced by the development of digital signal conditioning circuitry, such as microprocessors, having memory which can be readily erased and rewritten to contain the unique characteristics of a given sensing transducer. Unfortunately, entering data defining the unique characteristics of a given sensing transducer into a signal conditioner in a quick and convenient manner and free of operator errors remains a problem.
Methods of entering data defining the unique characteristics of a given sensing transducer into the memory of a microprocessor or other circuitry of a monitoring system have included keyboards; magnetic discs, tapes or cards; punched tapes or cards; and, tape or cards including bar codes. All of these prior art data entering techniques are prone to errors and/or inconveniences of one kind or another.
Keyboards are time consuming and highly subject to operator error. Discs, tapes and cards, whether magnetic, punched or bar coded, require some additional object to be associated with the sensor and used when the sensor is coupled to the signal conditioner. Each of these devices is subject to loss or damage in handling. In view of such problems, none of these prior art techniques is attractive for changing a sensing transducer in an environment where speed and accuracy is imperative. Such changes may be required, for example, in an operating room, when the cable interconnecting the sensing transducer to the signal conditioner is inadvertently severed or the transducer otherwise fails.
It is, thus, apparent that the need exists in monitoring systems utilizing sensing transducers having unique signal generating characteristics for an arrangement permitting a signal conditioner to be quickly and accurately calibrated or programmed for accurate operation with a new sensing transducer without the use of a manual keyboard or a separate disc, tape or card which must be associated with the sensing transducer.